The present invention relates generally to metal recovery methods and, more particularly, to the recovery of metal from oil shale and like materials. In another aspect, the invention relates to the treatment of oil shale in a manner such that metal values are recovered from one portion of shale starting material and the excess heat generated in the production of metal values from this portion of the shale is used for pyrolysis of the other portion of shale starting material for oil recovery therefrom.
The present invention represents an improvement, and in a certain respect, a variation of the methods of metal recovery which are described in U.S. Pat. Nos. 3,979,205 and 3,819,363. The method of the invention can be advantageously combined with known processes of oil shale pyrolysis.
As set forth in the patents referred to above, various carbonaceous land and sea ores are treated by various processes, all of which included the steps of treating the ore material with oxidizing and/or oxidizing and reducing agents, and then permitting the oxidized materials to ignite spontaneously to form a fine ash product. Metal values were recovered from the vapor phase of this process, or from the ash collected therefrom, or both.
According to the present invention, the starting material, instead of the type of carbonaceous ore referred to in the above patents, is oil shale, typically, Saskatchewan or Colorado oil shale. According to the invention, the oil shale serves as a starting material and furnishes metal values as well as most or all of the additional fuel and chemical products required to conduct the separation process. In one form of the invention, the shale is retorted indirectly and in the other form the shale is directly retorted. The process can be accomplished with no damage to the environment.
In view of the desire to obtain new and improved chemical processes and methods, particularly those which can be carried out in a manner compatible with the environment, and in view of the need to utilize abundantly available natural resources and to avoid depleting scarce resources, it is an object of the present invention to provide an improved metal recovery process.
Another object is to provide a metal recovery method wherein oil shale or other similar materials are used as the starting products in the process.
Another object is to provide a method of treating oil shale in which one portion of a mass of shale selected for treatment is exposed to a metal recovery method and wherein the other portion of the selected mass of material is pyrolyzed in a known manner, and in which the excess heat generated in the metal recovery portion of the process is used to aid in the recovery of oil by the pyrolysis method.
Yet another object is to provide a metal recovery method wherein the metals are recovered from a vapor phase which is produced by the combustion of treated oil shale or like products.
Still another object is to provide a method for recovering metal and other products from the solid phase ash produced by pyrolyzing or retorting oil shale or like products.
Still another object is to provide for recovery of alkalies and alkaline earth metal oxides during treatment of oil shale.
It is still a further object of the invention to remove sulfur compounds from the products of shale combustion by the use of materials derived from the shale or other starting materials.
Another object of the invention is to provide a method which makes optimum use of nitric and hydrochloric acids which are generated during the combustion process and to make use of the alakall and alkaline earth hydroxides generated in one portion of the process to form oxidizing agents which are used in other portions of the process.
A still further object is to provide a method wherein oxygen-containing chemicals and atmospheric oxygen are used to cause an exceedingly rapid rate of treated shale combustion with the production of great amounts of heat in order to drive the metals sought to be recovered into a vapor phase, and at the same time, to have extra heat available for use in associated chemical processes.
It is an object of this invention to operate either or both the oxidizing and pyrolysis chambers at extremely high temperatures and pressures, with continuous or batch feed, to produce high temperature - high pressure chemistry, very high combustion and production rates. Outputs in addition to vapor phase metal values and oil vapor include a full range of cracked oil products; synthesis products, such as SNG and other gases; ammonia and ammonia derivative products such as hydroxylamine, hydrazene, urea, thiourea, cynamide and guanidine; ash and heat.
It is an object of this invention to use added catalysts for the production of ammonia and ammonia-type products, and to crack the oil into its fractions, using added or autogenous natural catalytic agents under conditions of high temperatures and pressures.
The foregoing and other objects of the invention are achieved in practice by recovering oil shale or the like, reducing it to appropriate particle size, burning the shale or like material in the presence of oxygen containing compounds and air, separating the combustion products into an ash phase and a vapor phase which contains metal, subsequently treating both the vapor and solid ash phases for recovery of metals therefrom, and utilizing portions of the heat derived from the oxidation process to pyrolyze additional shale for recovery of oil therefrom. The invention also contemplates recovering some metal values from the solid pyrolysis products of shale, and using vapor phase oil from pyrolysis to oil in the collection of metals or metal compounds.
The exact manner in which the foregoing objects are carried into practice will become more clearly apparent when reference is made to the following detailed description of the preferred embodiments of the invention, set forth by way of example and shown in the accompanying drawings.